1. Field of the Invention
The present invention relates to an acoustic diaphragm vibrated by sound signal, radiating sound in the air, and a manufacturing process for the same.
2. Background Art
There is known a conventional acoustic diaphragm (1) which consists of mixed fabric made up of two or more kinds of synthetic or inorganic fibers with high elasticity. Additionally, a conventional plate-shaped acoustic diaphragm (2) is also known, made principally of wood, natural material. The plate-shaped acoustic diaphragm (2), for example, has been manufactured by the following manufacturing process.
After wood is first sliced, the hydroxyl groups of the sliced wood are substituted with acetic groups using acetic anhydride: the suctionality of the sliced wood is thus lost, resulting in increased size stability of the sliced wood. Then, plywood is made up of the sliced wood processed as above, and formed into the above-mentioned plate-shaped acoustic diaphragm (2).
It is necessary that the above-mentioned acoustic diaphragms have the characteristics of light weight and high stiffness, namely high specific elasticity ratio (E/.rho.) and high inner loss (tan .delta.) in order to display superior acoustic characteristics.
Since the above-mentioned conventional acoustic diaphragm (1) has a higher density (.rho.) than wood, it has a lower specific elasticity ratio (E/.rho.) than an acoustic diaphragm consisting of wood. Therefore, it is difficult to manufacture for increased stiffness a thick conventional acoustic diaphragm (1). Moreover, using for carbon fiber with high elasticity so as to manufacture the conventional acoustic diaphragm (1), it can have comparatively high specific elasticity ratio (E/.rho.) but inner loss (tan .delta.) is very low. As a result, at high frequencies, innate resonated peak is sharp, thus this conventional diaphragm does not display superior acoustic characteristics.
In contrast, the above-mentioned conventional acoustic diaphragm (2) is characterized with a high specific elasticity ratio (E/.rho.) and a superior acoustic. However, due to limitations concerning its planar plate-shape, it has the disadvantageous of that it is difficult to form curved solid shape of the conventional acoustic diaphragm (2), for example, a cone-shaped acoustic diaphragm for a speaker.
Consequently, due to increases which will occur in the production costs, the conventional processing technique cannot be applied to the manufacturing process for the conventional acoustic diaphragm (2). Moreover, due to the use of wood, natural material, material properties of the conventional acoustic diaphragm (2) as described above have the disadvantageous of being uneven and anisotropic.